Towards Clustered Carbonyl Cations [M(CO)] (M = Ru, Os): the Need for Innocent Deelectronation

To access the hitherto almost unknown class of clustered transition metal carbonyl cations, the trimetal dodecacarbonyls M(CO) (M = Ru, Os) were reacted with the oxidant Ag[WCA], but yielded the silver complexes [Ag{M(CO)}][WCA] (WCA = [Al(OR)], [F{Al(OR)}]; R = -OC(CF)). Addition of further diiodine I to increase the redox potential led for M = Ru non-specifically to divalent mixed iodo-Ru-carbonyl cations. With [NO], even the N-O bond was cleaved and led to the butterfly carbonyl complex cation [RuN(CO)] in low yield. Obviously, ionization of M(CO) with retention of its pseudo-binary composition including only M and CO is difficult and the inorganic reagents did react non-innocently. Yet, the radical cation of the commercially available perhalogenated anthracene derivative 9,10-dichlorooctafluoroanthracene (anthracene) is a straightforward accessible innocent deelectronator with a half-wave potential of 1.42 V Fc. It deelectronates M(CO) under a CO atmosphere and leads to the structurally characterized cluster salts [M(CO)]([WCA]) including a linear M chain. The structural characterization as well as vibrational and NMR spectroscopies indicate the presence of three electronically independent sets of carbonyl ligands, which almost mimic M(CO), free CO and even [M(CO)] in one and the same cation.